Activation analysis is an important method for elemental analysis, mainly because of its sensitivity. The accuracy and precision obtainable with charged particle activation analysis (CPAA) have been significantly improved. Standardization problems were studied thoroughly and the accuracy was demonstrated during various inter-laboratory and inter-method comparisons. Most of the applications of CPAA deal with the determination of light elements, such as hydrogen, carbon, nitrogen and oxygen, in metals and semi-conductors. Because a surface layer containing the activity formed at the surface can be removed by chemical etching after irradiation, CPAA has shown that for some metals the concentrations are orders of magnitude lower than expected on the basis of chemical analytical methods. CPAA was very often applied as a reference method for certification analyses.